Is it really beyond the realm of possibility that the lack of a blur filter would enable a sharper picture?

Nope, and no one said it wouldn't...just in the case of the D7100, it made no practical difference.

It does make some difference. As Reilly says, it gives sharper / crisper (not to be confused with more resolution) picture which, of course, disappears completely after applying some sharpening to D5200. Dpreview says so, and with correct words being used: D7100 delivers a more crisp file.

But, it does not really give more resolution which is the most important thing. For more resolution, I say again, you need more megapixels. Just compare D800 with both D7100 and D5200, it spanks both equally.

Where dpreview makes a mistake is saying that it's neutral to image quality. It's not. What they should say at the conclusion is that it does give a crisper picture than D5200, and that it does show significantly more artifacts than D5200 (look at the coin).